(a) Technical Field
The present invention relates to a polyamide resin composition having high heat resistance and oxidation resistance. The polyamide resin composition may include a polyamide copolymer having high heat resistance and high rigidity with citric acid and ethylenediaminetetraacetic acid (EDTA), which may rapidly cause surface oxidation with glass fiber, and form a highly dense oxide film on a polymer surface at high temperatures for a long time, thereby preventing oxidation and thermal decomposition by exterior oxygen and heat. In addition, the polyamide resin composition may have substantially improved excellent physical properties such as impact strength, tensile strength, flexural strength and elongation.
(b) Background Art
In recent plastic industry, materials have been required to have reduced weight, high resistance to elevated temperatures and high strength. In particular, for components for vehicles, the application of superior heat-resistant materials has been increased as the plastic materials have been exposed to highly elevated operating or surrounding temperatures thereof in reduced space. However, since plastic polymers are thermally decomposed upon continuous exposure to heat for an extended time, heat-resistance treatment to prevent oxidation and thermal decomposition thereof may be required for use under such conditions. For instance, nylon (PA66), as a representative aliphatic polyamide (PA), has been used in various industries to provide high mechanical strength, chemical resistance and heat resistance.
Among others, PA6T, which is a kind of semi-aromatic polyamide, has been used because it has greater heat resistance and less moisture absorption than nylon (PA66). However, PA6T has high melting point such that manufacturing using PA6T may not be efficient. For this reason, copolymers of PA6T with PA6I or nylon have been generally used for materials of vehicle components, such as fuses for engine rooms, connectors and mobile connectors, requiring high heat resistance and dimensional strength. However, when those components continuously exposed to a temperatures of 100° C. or greater, oxidation and thermal decomposition may occur, and essential properties such as strength and elongation as well as overall properties thereof may be significantly reduced, although each component of those polymers has a high melting point.
Accordingly, in the related arts, inorganic substances such as CuI or KI as heat-resistant treating agents and organic substances such as hindered amines or phenols as additives have been used. However, the effects of delaying oxidation and thermal decomposition have been obtained only upon temporary exposure to high temperatures without reducing oxidation and thermal decomposition. In addition, physical properties have been thus deteriorated upon exposure to high temperatures for extended time. In particular, when an amount of added heat-resistant treating agent is increased so as to improve long-term heat resistance, significant deterioration in basic physical properties may occur.
Accordingly, for extended use of engineered plastic polymers, which are lightweight and have superior shape molding and basic physical properties in the industries requiring high physical properties at high temperatures, as alternative to metals, development of technologies may be required to prevent oxidation and thermal aging of the polymers.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.